An air conditioning apparatus for a motor vehicle conventionally includes an air mixing chamber having two inlets, one for cooled air directly received from an evaporator and the other for heated air which has been passed over a heater core. A so-called "blend door" device pivots between a first position in which it substantially closes the first opening and a second position in which it substantially closes the second opening. Controls, such as hand-operated controls, set the position of the blend door either to one of the first or second positions, or to an intermediate position.
The air conditioning apparatus also has a number of outlets from the air mixing chamber, the outlets being connected via suitable conduits to different parts of the vehicle cabin, for example to the drivers side and to the passengers side.
A disadvantage of the known apparatus is that different temperatures exist within the air mixing chamber and thus that depending upon the location of the outlet within the chamber, different temperatures may be delivered to different parts of the vehicle cabin. The reason for the differing temperatures in the air mixing chamber lies in the different flow properties of the heated and the cooled air. Referring to FIG. 1, it will be seen that the cooled air arrives at a mixing chamber directly from the evaporator, whereas the heated air also emanates from the evaporator, but then passes through the heater core, which restricts air flow.
It will therefore be clear to one skilled in the art that with the conventional device the effect of the cooled air will predominate, at least on the left hand side, as shown in FIG. 1.
It is an object of the present invention to mitigate the above-mentioned difficulties.